ACPAtmospheric Chemistry and PhysicsACPAtmos. Chem. Phys.1680-7324Copernicus GmbHGöttingen, Germany10.5194/acp-13-3865-2013Oxidation of SO<sub>2</sub> by stabilized Criegee intermediate (sCI) radicals as a crucial source for atmospheric sulfuric acid concentrationsBoyM.1MogensenD.12SmolanderS.1ZhouL.1NieminenT.1PaasonenP.17Plass-DülmerC.3SipiläM.1PetäjäT.1MauldinL.145BerresheimH.6KulmalaM.11Department of Physics, P.O. Box 48, University of Helsinki, 00014 Helsink, Finland2Helsinki University Centre for Environment, P.O. Box 27, University of Helsinki, 00014 Helsink, Finland3Hohenpeissenberg Meteorological Observatory, German Weather Service, Hohenpeissenberg, Germany4Department of Atmospheric and Oceanic Sciences, University of Colorado at Boulder, P.O. Box 311, Boulder, Colorado 80309-0311, USA5Institute for Arctic and Alpine Research, University of Colorado at Boulder, P.O. Box 450, Boulder, Colorado 80309-0450, USA6Center for Climate and Air Pollution Studies, School of Physics, National University of Ireland Galway, Galway, Ireland7International Institute for Applied Systems Analysis (IIASA), Schlossplatz 1, 2361 Laxenburg, Austria1204201313738653879This work is licensed under a Creative Commons Attribution 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/This article is available from http://www.atmos-chem-phys.net/13/3865/2013/acp-13-3865-2013.htmlThe full text article is available as a PDF file from http://www.atmos-chem-phys.net/13/3865/2013/acp-13-3865-2013.pdf

The effect of increased reaction rates of stabilized Criegee
intermediates (sCIs) with SO<sub>2</sub> to produce sulfuric acid is
investigated using data from two different locations, SMEAR II,
Hyytiälä, Finland, and Hohenpeissenberg, Germany. Results
from MALTE, a zero-dimensional model, show that using previous
values for the rate coefficients of sCI + SO<sub>2</sub>, the model
underestimates gas phase H<sub>2</sub>SO<sub>4</sub> by up to a factor of two
when compared to measurements. Using the rate coefficients recently
calculated by Mauldin et al. (2012) increases sulfuric acid by
30–40%. Increasing the rate coefficient for formaldehyde oxide
(CH<sub>2</sub>OO) with SO<sub>2</sub> according to the values recommended by
Welz et al. (2012) increases the H<sub>2</sub>SO<sub>4</sub> yield by 3–6%.
Taken together, these increases
lead to the conclusion that, depending on their concentrations, the
reaction of stabilized Criegee intermediates with SO<sub>2</sub> could
contribute as much as 33–46% to atmospheric sulfuric acid gas
phase concentrations at ground level. Using the SMEAR II data,
results from SOSA, a one-dimensional model, show that the contribution
from sCI reactions to sulfuric acid production is most important in
the canopy, where the concentrations of organic compounds are the
highest, but can have significant effects on sulfuric acid
concentrations up to 100 m. The recent findings that the
reaction of sCI + SO<sub>2</sub> is much faster than previously thought
together with these results show that the inclusion of this new
oxidation mechanism could be crucial in regional as well as global
models.